SAN ANTONIO -- Women with early breast cancer had similar disease control and survival with accelerated partial breast irradiation (APBI) or whole-breast irradiation (WBI), the first time APBI has demonstrated noninferiority to WBI, a randomized trial showed.

Patients who received multicatheter brachytherapy APBI after lumpectomy had a 5-year local recurrence rate of 1.4% compared with 0.9% for women who had WBI. The 5-year disease-free survival (DFS) and overall survival were similar between treatment groups.

"These are daily practice-changing findings," said Strnad. "Partial breast irradiation, using multicatheter brachytherapy, can be considered a valid and effective option that can be offered for all low-risk breast cancer patients in routine clinical practice."

The incidence of serious late side effects was low in both treatment groups and did not differ significantly with the exception of grade 2/3 breast pain, which occurred more often with WBI than with APBI (3.17% versus 1.14%, P=0.0389). Grade 2/3 late skin effects occurred less often with APBI (3.2% versus 5.7%, P=0.08) and grade 2/3 subcutaneous tissue late effects slightly more often with APBI (7.6% versus 6.3%, P=0.53). No grade 4 late effects occurred in either group.

Cosmesis outcomes will be reported at a later date.

In an interview, Strnad told MedPage Today, "I really think these results have the potential to drive changes in the treatment of primary breast cancer. Partial breast irradiation using multicatheter brachytherapy really differs substantially from whole-breast irradiation. It is protective of surrounding tissues. Consequently, I believe that in the near future, perhaps 1 or 2 years, that if hospitals do not offer partial breast irradiation, they really can't treat early breast cancer."

Investigators in the study reported by Strnad used a specific type of APBI, noted Frank A. Vicini, MD, of 21st Century Oncology in Farmington Hills, Mich. APBI comprises multiple modes of radiation delivery, some of which involve external radiation therapy. The study showed that the concept of concentrating radiation on a small area leads to equivalent disease control and survival, offers the potential to reduce toxicity, and substantially reduces the time commitment for patients, to 4 days in the case of the technique used by Strnad and colleagues.

Vicini acknowledged that external radiation techniques continue to be favored in the United States, primarily because of wider availability of the technology and ease and familiarity of use. As women learn about the potential advantages of APBI, however, they will undoubtedly request it and more medical centers will offer it, he said.

Whether multicatheter brachytherapy or other techniques of truly local radiation delivery will prevail is hardly assured, according to Alphonse Taghian, MD, PhD, of Massachusetts General Hospital Cancer Center in Boston.

"[The study] proves the hypothesis that we might not need to treat the entire breast and that we can finish radiation therapy in around one weeks," Taghian said. "They used one particular technique, but there are others.

"It's like a horse race. Maybe you have 10 horses at the start and you don't know which one will be dominant until they start moving forward. At this point we don't know, but my guess is that external beam will be dominant because it is easier to use. It doesn't involve a learning curve like the technique they used in this study."

Strnad and Vicini acknowledged that the muticatheter technique requires training and practice, but in their opinion, the learning curve is not exceptionally steep.

Strnad reported findings from a phase III randomized trial involving 1,184 patients with low-risk stage 0-IIA breast cancer, enrolled at centers in Germany, Hungary, Poland, and Spain. All the patients underwent breast-conserving surgery and then were randomized to APBI or WBI. The primary endpoint was local recurrence. Secondary endpoints included DFS, overall survival, toxicity, and cosmesis.

The trial was statistically powered for noninferiority, and after a median follow-up of 6.6 years, the results demonstrated that the 5-year local recurrence rate with APBI was not inferior to that of women treated with WBI (P=0.42). The 5-year DFS was 95.0% with APBI and 94.5% with WBI, and 5-year overall survival was 97.3% in the APBI arm and 95.6% among women randomized to WBI.

The study was supported by German Cancer Aid.

Strnad disclosed relationships with German Cancer Aid and with Nucleotron Operations, a subsidiary of Elekta.

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